[petsc-users] Is it possible to keep track of original elements # after a call to DMPlexDistribute ?

[Matthew Knepley]

On Wed, Jul 14, 2021 at 1:18 PM Eric Chamberland <
Eric.Chamberland at giref.ulaval.ca> wrote:

> Hi,
>
> I want to use DMPlexDistribute from PETSc for computing overlapping and
> play with the different partitioners supported.
>
> However, after calling DMPlexDistribute, I noticed the elements are
> renumbered and then the original number is lost.
>
> What would be the best way to keep track of the element renumbering?
>
> a) Adding an optional parameter to let the user retrieve a vector or
> "IS" giving the old number?
>
> b) Adding a DMLabel (seems a wrong good solution)
>
> c) Other idea?
>
> Of course, I don't want to loose performances with the need of this
> "mapping"...
>

You need to call

  https://petsc.org/release/docs/manualpages/DM/DMSetUseNatural.html

before call DMPlexDistribute(). Then you can call


https://petsc.org/release/docs/manualpages/DMPLEX/DMPlexGlobalToNaturalBegin.html

to map back to the original numbering if you want. This is the same thing
that DMDA is doing.

  Thanks,

     Matt


> Thanks,
>
> Eric
>
> --
> Eric Chamberland, ing., M. Ing
> Professionnel de recherche
> GIREF/Université Laval
> (418) 656-2131 poste 41 22 42
>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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